In the past, there have been several techniques attempted to be utilized by commercial tuna fishermen to separate dolphin from tuna. Tuna fishermen in small boats in advance of the nets have attempted to chase the dolphin away from the nets and this technique has resulted in the injury and possible loss of life to tuna fishermen and still results in some dolphin being caught in tuna nets. Others have attempted explosions in the water to frighten the dolphin.
The present invention utilizes the primordial fear of dolphin to killer whale to separate dolphin from tuna. This permits the tuna to be caught in tuna nets without the dolphin being captured in the tuna net. According to the invention, the sound of one or more killer whale feeding is captured by a transducer, converted to digital sound and then edited to edit out splashing sounds or other non-useful portions of the recording. In addition, the killer whale feeding sounds are enhanced by producing more of them and, when such killer whales are in a feeding frenzy, the sounds are recorded digitized, edited and enhanced and then broadcast in the sea water by a high power acoustic transducer to simulate the feeding frenzy.
In the preferred embodiment, these enhanced feeding sounds of killer whales are digitally stored and reproduced in an underwater transducer. The transducer (there may be a plurality of spaced transducers to simulate more than one killer whale) is positioned ahead of a net which is being used to capture the tuna. In another embodiment, the transducer(s) is located between the net and the ship towing the net. Preferably, the transducer is located along the travel axis or path of the ship and the net.